Circuit breaker

ABSTRACT

A circuit breaker wherein a pair of valves having different diameters are connected with each other through an actuating rod so as to constitute first differential valve means, a valve seat having a diameter smaller than that of the smaller-diameter valve is provided in the larger-diameter valve in such a manner as to be able to be brought into and out of contact with the largerdiameter valve, second differential valve means is established between the smaller-diameter valve and the effective minimum diameter given by the contact of the valve seat with the largerdiameter valve so that pressure medium always acts on these two valves, the aforementioned two differential valve arrangements are reversed through the engagement and disengagement of the valve seat and by controlling the pressure of the medium acting on the larger-diameter valve by means of a controller, whereby the aforementioned actuating rod is biased either in the closing direction or breaking direction, and thus the breaking portion connected with the actuating rod is operated.

United States Patent [191 Nakano June 12, 1973 CIRCUIT BREAKER [75] Inventor:

[73] Assignee: Hitachi, Ltd., Tokyo, Japan [22] Filed: Nov. 16, 1971 [21] Appl. No: 199,194

Zenichi Nakano, Hitachi, Japan Primary ExaminerRobert S. Macon Attorney-Craig, Antonelli and Hill [57] ABSTRACT A circuit breaker wherein a pair of valves having different diameters are connected with each other through an actuating rod so as to constitute first differential valve means, a valve seat having a diameter smaller than that of the smaller-diameter valve is provided in the larger-diameter valve in such a manner as to be able to be brought into and out of contact with the largerdiameter valve, second differential valve means is established between the smaller-diameter valve and the effective minimum diameter given by the contact of the valve seat with the larger-diameter valve so that pressure medium always acts on these two valves, the aforementioned two differential valve arrangements are reversed through the engagement and disengagement of the valve seat and by controlling the pressure of the medium acting on the larger-diameter valve by means of a controller, whereby the aforementioned actuating rod is biased either in the closing direction or breaking direction, and thus the breaking portion connected with the actuating rod is operated.

10 Claims, 7 Drawing Figures F'UU 2 1 Dunn.

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INVENTOR ZENICHI NAKAN BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a circuit breaker, and more particularly to the operating mechanism of such a breaker.

2. Description of the Prior Art As a result of the recent increasing demand for electric power, the capacity of the transmission network as well as the amount of generated energy has become insufficient to cope with such demand. Under such circumstances, if any short-circuit accident occurs with the high power system and it persists, then the relations between supply and demand become unbalanced so that the system becomes disturbed, thus making it impossible to achieve stable power transmission. If such a condition should be left as it is, then the system would be stopped in succession so that the electric power sys tem would become completely paralized Therefore, it is essential that any accident which has occurred in the system be eliminated froM the system in a very short time. For this reason, a quicker breaking function, in other words, a reduction of the opening time is more urgently required for circuit breakers serving as protecting devices for such systems.

Especially in the case of circuit breakers adapted to handle a high voltage, the breaking portion thereof is located at a considerably high level in order to electrically isolate the breaking portion assuming a high potential from ground, and as a result the distance over which a signal for operating the breaking portion is to be transmitted becomes relatively long.

In the case of mechanical operation, the transmission of the operating signal is performed by means of an insulating rod, with insulation in view. There has been proposed a method of relatively reducing the operating time by maintaining the insulating rod under preliminary resilient tension, that is, resilient deformation and releasing the insulating rod upon receipt of a breaking command.

SUMMARY OF THE INVENTION It is a primary object of this invention to provide a circuit breaker of which the operating time is reduced by a nOvel method.

Another object of this invention is to provide a circuit breaker including an operating mechanism wherein the number of intermediate amplifying stages for actually operating the operational mechanism in accordance with a breaking command is reduced so that the mechanism is simplified and hardly subject to trouble.

Still another object of this invention is to provide a circuit breaker capable of operating the breaking portion with extremely small signal energy relative to large energy.

According to this invention, there is provided a circuit breaker including an operating mechanism wherein a first differential power relationship is established by a pair of pressure means adapted to produce forces of different magnitudes directed in opposite directions and connected with each other through an actuating rod, a second differential power relationship is established between the pressure means adapted to produce the higher force and the pressure means adapted to produce the smaller force by reducing the higher force by detachably providing force reducing means in the higher force producing means, and these two differential power relationships are made to rise and fall or reversed by controlling the attachment and detachment of the force reducing means to the higher force producing means, whereby the actuating rod is biased either in the closing direction or breaking direction and thus the breaking portion is operated.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view showing the circuit breaker according to an embodiment of this invention.

FIG. 2 is a partial longitudinal sectional view showing the earth tank of the circuit breaker shown in FIG. 1.

FIG. 3 is an enlarged view showing a modification to a portion of FIG. 2.

FIGS. 4 and 5 are partial longitudinal sectional views showing the circuit breakers according to a Second and a third embodiment of this invention, respectively.

FIG. 6 is an enlarged view showing a modification to a portion 0F FIG. 5.

FIG. 7 is a partial longitudinal sectional view showing the circuit breaker according to a fourth embodiment of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS ReFerring to FIG. 1, there is shown an air-blast circuit breaker based on the principles of this invention, wherein there is provided an earth tank 11 provided with a plurality of porcelain tubes 12a and 12b to which are fixedly secured breaking portions 13a to 13d respectively which are maintained at high potentials. In this case, the porcelain tubes 12a to 12d are provided for the purposes of supporting the breaking portions 13a to 13d and at the same time electrically insulating them from the earth tank 11.

Into the breaking portions are introduced electric currents through pairs of bushings 14a and 15a, 14d and 15d each consisting of porcelain; in the case where the arrangement of the breaking portions is of the two-point breaking type and the breaking portions 13a to 13d are connected in series with each other, voltage dividing condensers 16a, 17a 16d, 17d are provided for the purpose of making uniform the breaking capacity at each breaking point.

With a circuit breaker handling a high voltage, a closing or breaking resistor is in some cases added to each of the breaking points 13a to 13d but it is not shown in the drawings.

In the case of an air-blast circuit breaker, it is the usual practice that compressed air which has been used for the purpose of effecting extinction of arc is discharged into the open air. In such a case, the speed that the compressed air is discharged may sometimes become as high as the speed of sound so that noise may be produced; in order to cope with this, silencers 18a to 18d are associated with the breaking portions 13a to 13d respectively.

The air-blast circuit breaker of the foregoing construction is supported at a position of a predetermined height above the ground surface by means of a base 19 supporting the earth tank 11.

The operating mechanism for the breaking portions to 13d is contained in the earth tank 11, and it is controlled either in the closing or breaking direction by means of an operating valve box provided in the axial end portion of the earth tank 11.

The operating mechanism contained in the earth tank 11 will be described with reference to FIG. 2.

At the opposite axial ends of the earth tank 11 are provided a valve box 21 and a valve box 22 formed by the flange portion of the earth tank 11. In the valve box 21, there is an air-tight and yet slidably provided pressure means having a high force such for example as a larger-diameter valve 23 having a diameter of A, and in the valve box 22 there is pressure means having a low force such for example as a smaller-diameter valve 24 having a diameter B. The larger-diameter valve 23 and smaller-diameter valve 24 are positioned in such a relationship that the diameter A of the former is larger than the diameter B of the latter, and these valves 23 and 24 are connected with each other through an actuating rod 25 extending through the earth tank 11 in such a manner as to establish a first differential power relationship. Such a differential power relationship may also be established by valves associated with the respective breaking portions (by receiving valves provided in the breaking portions, for example).

The actuating rod 25 is coupled to an insulating rod 28 extending through the porcelain tube 12a by means of a coupling fixture 26 and L-shaped link 27, so that the insulating rod 28 is moved upwards and downwards through the movement of the actuating rod 25 whereby the breaking portion 130 is operated.

The larger-diameter valve 23 is provided with a valve seat packing of which the diameter C is smaller than the diameter B of the smaller-diameter valve 24. Provided within the valve box 21 is force reducing means such as valve seat 29 so that it may be disposed into and out of engagement with the valve seat packing. When the valve seat 29 is brought into contact with the largerdiameter valve 23, the effective area of the largerdiameter valve 23 is given in terms of the diameter C of the valve seat (minimum effective diameter) as will be described later. Thus, a second differential power relationship is established between the diameters B and C of the larger-diameter valve 23 and smaller-diameter valve 24 by exhausting high pressure air acting on the outside of the valve seat, as will be described hereinafter.

Furthermore, the valve seat 29 has flange portions 29A and 298 provided on the inner and outer peripheral surfaces thereof respectively. The inner flange portion 29A has a spring 30 interposed between itself and the valve box 21 whereby the valve seat 29 is always made to follow the larger-diameter valve 23, and the outer flange portion 298 is disposed in close contact with the inner surface of the valve box 21 so as to constitute a piston surface.

A space a defined by the valve box 21, largerdiameter valve 23 and valve seat 29 and a space B defined by the valve box 21 and inner flange portion 29B of the valve seat 29 are in communication with the operating valve box 20 provided adjacent the valve box 21 through holes 21A and 21B formed in the valve box 21.

Air compressed at 30 atmospheric pressures for example is pumped into the earth tank 11 so that the compressed air reaches the breaking portion 13a, passing through the porcelain tube 12a so as to be ready to be blown onto an arc when breaking instruction is given. At the same time, the compressed air acts on the larger-diameter valve 23 and smaller-diameter valve 24. The opposite sides of the valves 23 and 24 are exposed to the atmosphere. The space a is at a low pressure (in this case, under the atmospheric pressure), whereas the space B is at a pressure equal to that of the compressed air filled in the earth tank 11. The space 'y is also under the pressure equal to that of the compressed air through communicating hole 290 formed in the valve seat 29. As a result, the valve seat 29 is brought into contact with the valve seat packing of the larger-diameter valve 23 by the spring 30 and a force produced from the difference between the area corresponding to the inner diameter at which the valve seat 29 contacts the valve box 21 and that corresponding to the minimum effective diameter C at which the valve seat 29 contacts the larger-diameter valve, multiplied by the pressure of the compressed air. Thus, the second differential power relationship is established, so that the larger-diameter valve 23 and smaller-diameter valve 23 are biased to the left, that is, to the closing position.

When a breaking instruction is given in accordance with which breaking an electromagnetic valve accommodated in the operating valve box 20 is operated so that the compressed air in the space B is exhausted into the atmosphere, the valve seat 29 is moved to the right against the spring 30 by the difference between the pressure of the compressed air acting on the tubular portion of the valve seat and that acting on the outer flange portion thereof, with the result that the valve seat 29 is separated from the valve seat packing of the larger-diameter valve 23 and the compressed air contained in the earth tank 11 acts on the entire surface of the larger-diameter valve 23. Thus, the differential power relationship between the larger-diameter valve 23 and the smaller-diameter valve 24 is reversed. That is, the second differential power relationship has initially be established, but upon establishment of the first differential power relationship resulting from the separation of the valve seat 29, the valves 23 and 24 are moved to move the insulation rod 28 downwardly, so that the breaking portion 13a is operated.

In the foregoing operation, the second differential power arrangement at the closing position can be achieved simply by holding the closing position, so that the differential ratio can be made extremely low. Accordingly, the space B required for bringing the valve seat 29 into contact with the larger-diameter valve 23 can be greatly reduced so that the compressed air in the space B can be exhausted with a very small signal energy. Immediately after the valve seat 29 has been actuated, compressed air acts on the larger-diameter valve 23 so that the latter is moved to the left. At this point, it is possible to momentarily render the first differential power arrangement operative to the left by increasing the differential ratio of the first differential power arrangement, or by increasing the diameter A of the larger-diameter valve 23.

As will be appreciated from the foregoing, operating energy required for the breaking operation is available directly from an extremely small signal energy resulting from the exhausting of the air present in the space [3. Thus, it is possible to eliminate the conventional mechanism for amplifying such signal energy so as to provide operating energy, thus avoiding time lag which tends to occur in such an amplifying mechanism. This is very effective in an attempt to reduce the operating time, be-

cause in the case of a circuit breaker which requires high operating energy, that is, which requires a very high voltage and high breaking speed, the amplifying mechanism is constructed in the multi-stage type. As compared with the operating time reduction achieved through the elimination of the amplifying mechanism, the operating time reduction which is achieved by using preliminary resilient tension as in the prior art is only small; the insulating rod 28 shown in FIG. 1 is not provided with any preliminary resilient tension, but if necessary, a valve associated with the smaller-diameter valve 24 may be provided at the front end of the largerdiameter so that a differential relationship may be established between the larger-diameter valve 23 and the valve seat 29, thus imparting preliminary resilient tension to the insulating rod.

The breaking electromagnetic valve contained in the operating box not shown in detail is so designed as to be closed after it has been operated for a predetermined period of time in accordance with a breaking instruction imparted thereto, that is, when the compressed air in the space B has been exhausted. The space [3 is gradually charged with air after the breaking operation has been performed, so that the valve seat 29 is moved to the left by the spring force of the spring so as to be brought into contact with the valve seat packing of the larger-diameter valve 23. At this time, the closing electromagnetic valve remains inoperative. Thus, the action of the compressed air on the largerdiameter valve 23 is only such that the space a and the hole extending from the space a to the closing electromagnetic valve are charged with compressed air, whereby the larger-diameter valve 23 and the operating system connected therewith are made to remain at their leftward moved positions. For the closing operation, the closing electromagnetic valve in the operating box 20 is operated so that the compressed air filled in the space a is exhausted, the second differential power arrangement is again established which is defined by the diameter B of the smaller-diameter valve 24 and the diameter C of the valve seat, the larger-diameter valve 23 is returned to the closing position shown in the drawing, and the insulating rod 28 is upwardly moved through the actuating rod 25. In this way, the breaking portion 13a is closed.

As described above, according to this invention, the circuit breaker can be operated in a short time simply by means of signal energy required for driving the closing and breaking electromagnetic valves, without providing any amplifier mechanism in the intermediate stage. In addition, the operating mechanism is simplified, little subject to trouble and free from operational error.

FIG. 3 shows a modification to the small pressure means shown in FIG. 2, wherein the earth tank 11 has the ends thereof completely closed, and a compression spring 32 is interposed between the flange portion 11A of the earth tank 11 and a spring shoe 31 provided on the actuating rod 25.

Like the compressed air acting on the smallerdiameter 24 in FIG. 2, the force of the compression spring acts on the spring shoe 31 so that the first differential power relationship is established between the larger-diameter valve 23 and the smaller-diameter valve 24. This differential relationship is made to rise and fall or reversed according to whether the valve seat 29 is disposed into or out of contact with the valve seat parking.

In the foregoing, description has been made of the case where use is made of a compression spring as the spring 32; however, exactly the same effect can be produced also by means ofa tension spring provided opposite the spring shoe 31 provided on the actuating rod 25.

With reference to FIG. 4, description will now be made of an example wherein the principles of the present invention have been applied to a double pressure type gas breaker. In this case, high pressure gas which is used for the breaking purpose my be permitted to act on the respective valves, but description will be made of the case where the larger-diameter valve is operated by other compressed mediums such as for example pressure oil.

A porcelain tube 43 for high pressure gas is provided in parallel with a porcelain tube 42 extending upwardly from a low pressure side earth tank 41, and a breaking portion 44 is provided between these porcelain tubes.

High-temperature gas used for extinction of arc in the breaking portion 44 is cooled down in a cooler 45, passed to the low-pressure side earth tank 41 through the porcelain tube 42 provided for the purpose of passing low pressure gas therethrough, compressed in a compressor 46 and again returned to the porcelain tube 43 for high pressure gas. This means that there is formed a circulation path for the gas.

Provided below the porcelain tube 43 for highpressure gas are a valve box 47 filled with pressure oil and an oil pressure controller 48.

In the valve box 47, there are provided a largerdiameter valve 49 serving as transmitting valve, a valve seat 50 and a spring 51. Further, in the breaking portion 44, there is provided a smaller-diameter valve 49 serving as receiving valve of which the valve box 52 is constituted by the container flange portion of the breaking portion 44. The larger-diameter valve 49 and smaller-diameter valve 53 are connected with each other by the actuating rod 54 extending through the porcelain tube.

In this case, the insulating rod 54 is preferably made of an insulating material.

With the foregoing arrangement, the actuating rod 54 is adapted to serve as an insulated operating rod and provided with preliminary resilient tension by the valves 49 and 54.

It is pressure oil that acts on the larger-diameter valve 49, and it is gas for extinction of are that acts on the smaller-diameter valve 53. In case the pressures of these pressure liquids are different, such difference should be taken into consideration in order to determine the diameter of the larger-diameter valve, the diameter of the valve seat and the diameter of the smaller-diameter valve which establish the two differential power relationships. In order to prevent the pressure oil and gas from being mixed, it is necessary to provide a hermetically sealing slide portion 55 on part of the actuating rod 54.

A hole 47A formed in the valve box 47 is provided the valve seat 50; a hole 478 is provided for the purpose of operating the larger-diameter valve 49 when the closing operation is to be performed; and a hole 47C is provided for the purpose of always supplying pressure oil into the valve box 47.

Movement of the actuating rod 54 is effected exactly in the same way as described above in connection with FIG. 1, and therefore description thereof will be omitted. The movement of the actuating rod 54 results in rotational energy imparted to a rotary rod of the breaking portion 44 where by the breaking portion is operated.

In the foregoing, description has been made of the case where oil pressure is employed with respect to the larger-diameter valve 47; however, it is also possible that either compressed air or compressed gas may be utilized. In FIG. 4, reference numeral 56 represents a current introducing bushing.

Referring to FIG. 5, there is shown an example wherein the principle of this invention has been applied to a gas breaker for a substation and yet the valve seat is electromagnetically operated.

Supported within an earth tank 61 are two puffer type breaking portions 64 and 65 by means of a pair of insulating supporters 62 and 63. An electric current is introduced into the breaking portions 64 and 65 through a pair of bushings 66 and 67 in such a manner as to flow through the puffer type breaking portions to the bushing 67 by way of a fixed contact 65-movable contact 69 puffer cylinder 70 formed integrally with the movable contact puffer piston 71.

The puffer cylinder 70 is connected through an L- shaped link 73 with an insulating rod 72 extending through an insulating cylinder 85, and the insulating rod 72 is connected through an L-shaped link 76 with an actuating rod 75 extending through a metallic cylinder 74.

The actuating rod 75 has its lower end coupled to a larger-diameter valve 78 contained in a valve box 77 provided at the lower end of the earth tank 61, the upper end of the actuating rod 75 being coupled to a smaller-diameter valve 79 adapted for sliding hermetically with respect to the metallic cylinder 74. A valve seat 80 is provided in such a manner that it may be brought into and out of contact with the largerdiameter valve 78 through a spring 81, as described above.

Gas of high breakdown voltage is filled in the earth tank 61, with the view of increasing the creeping breakdown voltage of the breaking portions 6 1, 65, bushings 66, 67 and so forth; arc extinguishing gas is filled under a predetermined pressure in the breaking portions 641, 65, insulating cylinder 85 and metallic cylinder 74; and pressure oil is introduced into the valve box 77 from an oil pressure controlling device 82 through the hole 77A. In order to prevent the pressure gas and oil from being mixed, sealing means is provided at each necessary position.

The pressure oil acts on the larger-diameter valve 78, and the gas acts on the smaller-diameter valve 79, and the determination of the diameters of these valves has already been explained with respect to the embodiment shown in FIG. 2.

In breaking operation, the valve seat 80 is magnetically attracted upwardly by the fact that an electric current is passed through an electromagnetic coil 83 provided in the valve box 77 for a predetermined period of time, so that the valve seat 80 is separated from the larger-diameter valve 78. Thus, the puffer cylinder 70 and movable contact 69 are operated upwardly through the actuating rod 75 and actuating rod 72, so that arc occurring between the contacts 68 and 69 is extinguished by the compressed arc-extinguishable gas which is jetted thereto by means of the puffer cylinder and puffer piston 71. In this way the breaking operation is completed.

The movement of the valve seat and closing operation are the same as in the foregoing embodiments, and therefore description thereof will be omitted.

In order to drive the valve seat 80, it is possible to use an electromagnetic repulsive force. In such a case, the valve seat 80 is formed by a conductor material, and the electromagnetic geometric center X of the valve seat 80 is located at a position apart from the electromagnetic geometric center Y of the electromagnetic coil 83 relative to the larger-diameter valve 78, the distance 8 between these centers being kept extremely small.

Assume now that a breaking signal is imparted to the electromagnetic coil 83 so that an electric current flows therethrough, the resulting flux crosses the valve seat 80 in which, according to the Lenzs law, an electric current is induced which tends to cancel out this magnetic flux, and these currents flow in opposite directions so that there is produced a repulsive force by which the valve seat 80 is driven to be spaced apart from the larger-diameter valve 78.

The operations of the respective portions after the valve seat 80 has been separated from the largerdiameter valve 78 are exactly the same as described above in connection with FIG. 5.

In the foregoing, description has been of the cases where the operating mechanism according to this invention was located in the earth tank maintained at the ground potential or alternatively in both of the earth tank and electrically loaded portion; however, with reference to FIG. 7, description will now be made of the circuit breaker provided only in the electrically loaded portion.

A porcelain tube 101 is provided on the earth tank resting on the support base in such a manner as to extend upwardly therefrom, as in the case of FIG. 1, and

a bracket 102 is fixedly secured to the porcelain tube Valve boxes 103 and 104 of different inner diameters are provided between the opposite ends of the bracket 102, and a larger-diameter valve 106 and smallerdiameter valve 107 which are connected with each other by an actuating rod are slidably mounted in the valve boxes 103 and 106 respectively.

A valve seat 108 is detachably attached to the largerdiameter valve 106 by means of a spring having one end thereof fixed to a spring shoe 109 of the actuating rod 105.

The shoe for the spring 110 may be one fixed to the bracket 102 as shown in FIG. 2.

Compressed air is filled in the bracket 102 from the earth tank (not shown) through the porcelain tube 101, with a result that the first differential power relationship is established between the larger-diameter valve 106 and the smaller-diameter valve 107 and a second differential power relationship is established between the smaller-diameter valve 107 and the larger-diameter valve 106 in the range given by the minimum effective diameter controlled by the valve seat 108. Rise and fall or reversal of the two differential power relationships is effected by the valves 113 and 114 which are controlled by insulated operating rods 111 and 112 extending through the porcelain tube 101 respectively.

The valve 113 is opened by the insulated operating rod 111 being operated from the earth side, so that compressed air is a small space e defined by the inner cylinder 115 of the bracket 102 and valve seat 108 is exhausted in the atmosphere, whereby the valve seat 108 is moved to the left against the spring 110. Thus, compressed air acts on the entire surface of the largerdiameter valve 106 so that the first differential power relationship is established, and the actuating rod 105 is momentarily moved to the right.

Thereafter, the valve seat 108 is brought into engagement with the larger-diameter valve 106 by the spring 110.

When the insulated operating rod 112 is operated, the valve 119 is opened so that compressed air in a space (15 defined by the valve box 103, larger-diameter valve 106 and valve seat 108 so that the second differential power relationship is established, and the actuating rod 105 is moved to the left.

Secured to the bracket 102 is a puffer type breaking portion 117 similar to that shown in FIG. by means of a support structure 116, and it has the movable portion thereof coupled directly to the actuating rod 105 so as to be actuated either in the breaking direction or closing direction according to whether the aforementioned two differential power relationships are made to rise and fall or reversed.

in this case, electric current is permitted to flow from a terminal plate 118 provided on the breaking portion 117 to a terminal plate 119 provided on the bracket 102, passing through the breaking portion 117, support structure 116 and bracket 102.

For the foregoing operation, the space 6 may be very small, that is, it may be reduced to such an extent as required for the movement of the valve seat 108, and the valve 113 may also be a small one. Thus, little or no force is imparted to the insulated operating rod 111, and it can actuate the valve 113 without being subject to resilient deformation, even if preliminary resilient force is not imparted thereto. Furthermore, in order that the dead space extending from the space 6 to the valve 113 may be minimized, the valve 113 is provided closely adjacent to the space s so that the compressed air in the space 6 may be momentarily discharged into the atmosphere. Thus, the opening time of the breaking portion 117 can be reduced greatly as compared with the case of FIG. 1.

By using as valves 113 and 114 electromagnetic valves which are adapted to be operated directly by a breaking signal or closing signal, it is possible to eliminate the insulated operating rods 111 and 112. Furthermore, it is also possible to eliminate dead time tending to stem from play required for the actuation of the insulated operating rods 111 and 112 or time required for converting electric signal to mechanical signal. Thus, the opening time can be further reduced.

I claim:

1. A circuit breaker wherein a breaking portion is operated by biasing an actuating rod associated therewith either in the closing direction or breaking direction, said breaker comprising, a pair of pressure means having higher force producing means and lower force producing means connected through the actuation rod in opposing relationship to each other for producing a first differential force, force reducing means detachably provided in said higher force producing means, said higher force producing means when attached with said force reducing means being operable to cooperate with said lower force producing means to produce a second differential force, the directions of said first and second differential forces being opposite with each other, and control means for attaching or detaching said force reducing means to or from said higher force producing means thereby controlling the application of said first differential force or said second differential force to said actuating rod so as to render said actuating rod to be biased either in the closing direction or breaking direction.

2. A circuit breaker according to claim 1, wherein said pair of pressure means comprises a pair of valves of different diameters composing a first differential valve means to produce said first differential force, and said force reducing means comprises a valve seat having a diameter smaller than that of the smaller-diameter valve of said pair of valves, a second differential valve means for producing said second differential force being established between said smaller-diameter valve and the larger-diameter valve attached with said valve seat.

3. A circuit breaker according to claim 1, wherein said pair of pressure means comprises a valve on which a fluid pressure is acting and a spring, the fluid pressure force produced by said valve being larger than that of opposing spring force thereby producing said first differential force, and said force reducing means comprises a valve seat, the fluid pressure force produced by said valve when attached with said valve seat being smaller than the opposing force thereby producing said second differential force.

4. A circuit breaker according to claim 1, wherein said first differential force is made greater while said second differential force is made smaller, and said actuating rod is biased in the breaking direction when said first differential force is applied thereto while it is biased in the closing direction when said second differential force is applied thereto.

5. A circuit breaker according to claim 1, wherein said pair of pressure means together with said force reducing means for producing said first and second differential forces are provided in the breaking portion, and said control means is provided in an earth potential portion.

6. A circuit breaker according to claim 1, wherein said pair of pressure means comprises a pair of valves, the fluid pressures acting on said pair of valves are directed in opposite directions and are different in magnitude from each other thereby producing said first differential force, and said force reducing means comprises a valve seat detachably provided in one said pair of valves which produces larger force than the other.

7. A circuit breaker according to claim 6, wherein the pressure fluids acting on said pair of valves are constituted by different mediums.

8. A circuit breaker according to claim 2, wherein the larger-diameter valve of said pair of valves is provided as transmitting valve in the earth potential portion and the smaller-diameter valve is provided as receiving valve in the breaking portion, and said actuating rod is adapted to serve as insulated operating rod to which preliminary resilient tension is imparted by means of pressure fluids acting on said valves.

9. A circuit breaker according to claim 2, wherein said valve seat of said force reducing means has a flange adapted to substantially hermetically slide on the on the opposite surfaces of said flange, the space defined by said valve box surface on which said flange slides and said valve seat is reduced-to such an extent as required for the movement of said valve seat, a valve for controlling the pressure fluid acting on the opposite surfaces of said flange is provided closely adjacent to said valve seat, and a dead space extending from said space to said valve for controlling is as greatly reduced as possible. 

1. A circuit breaker wherein a breaking portion is operated by biasing an actuating rod associated therewith either in the closing direction or breaking direction, said breaker comprising, a pair of pressure means having higher force producing means and lower force producing means connected through the actuation rod in opposing relationship to each other for producing a first differential force, force reducing means detachably provided in said higher force producing means, said higher force producing means when attached with said force reducing means being operable to cooperate with said lower force producing means to produce a second differential force, the directions of said first and second differential forces being opposite with each other, and control means for attaching or detaching said force reducing means to or from said higher force producing means thereby controlling the application of said first differential force or said second differential force to said actuating rod so as to render said actuating rod to be biased either in the closing direction or breaking direction.
 2. A circuit breaker according to claim 1, wherein said pair of pressure means comprises a pair of valves of different diameters composing a first differential valve means to produce said first differential force, and said force reducing means comprises a valve seat having a diameter smaller than that of the smaller-diameter valve of said pair of valves, a second differential valve means for producing said second differential force being established between said smaller-diameter valve and the larger-diameter valve attached with said valve seat.
 3. A circuit breaker according to claim 1, wherein said pair of pressure means comprises a valve on which a fluid pressure is acting and a spring, the fluid pressure force produced by said valve being larger than that of opposing spring force thereby producing said first differential force, and said force reducing means comprises a valve seat, the fluid pressure force produced by said valve when attached with said valve seat being smaller than the opposing force thereby producing said second differential force.
 4. A circuit breaker according to claim 1, wherein said first differential force is made greater while said second differential force is made smaller, and said actuating rod is biased in the breaking direction when said first differential force is applied thereto while it is biased in the closing direction when said second differential force is applied thereto.
 5. A circuit breaker according to claim 1, wherein said pair of pressure means together with said force reducing means for producing said first and second differential forces are provided in the breaking portion, and said control means is provided in an earth potential portion.
 6. A circuit breaker according to claim 1, wherein said pair of pressure means comprises a pair of valves, the fluid pressures acting on said pair of valves are directed in opposite directions and are different in magnitude from each other thereby producing said first differential force, and said force reducing means comprises a valve seat detachably provided in one said pair of valves which produces larger force than the other.
 7. A circuit breaker according to claim 6, wherein the pressure fluids acting on said pair of valves are constituted by different mediums.
 8. A circuit breaker according to claim 2, wherein the larger-diameter valve of said pair of valves is provided as transmitting valve in the earth potential portion and the smaller-diameter valve is provided as receiving valve in the breaking portion, and said actuating rod is adapted to serve as insulated operating rod to which preliminary resilient tension is imparted by means of pressure fluids acting on said valves.
 9. A circuit breaker according to claim 2, wherein said valve seat of said force reducing means has a flange adapted to substantially hermetically slide on the surface of a valve box, and said valve seat is attached to or detached from said larger-diameter valve depending upon the difference between the fluid pressures acting on the opposite surfaces of said flange.
 10. A circuit breaker according to claim 2, wherein said valve seat of said force reducing means has a flange adapted to substantially hermetically slide on the surface of a valve box, said valve seat is attached to or detached from said larger-diameter valve depending upon the difference between the fluid pressures acting on the opposite surfaces of said flange, the space defined by said valve box surface on which said flange slides and said valve seat is reduced to such an extent as required for the movement of said valve Seat, a valve for controlling the pressure fluid acting on the opposite surfaces of said flange is provided closely adjacent to said valve seat, and a dead space extending from said space to said valve for controlling is as greatly reduced as possible. 